4-83 Consider a building in New York (40°N latitude) that has 76 m² of window area on its south wall. The windows are double-pane heat-absorbing type, and are equipped with light-colored vene- tian blinds with a shading coefficient of SC = 0.30. Determine the total solar heat gain of the building through the south windows at solar noon in April. What would your answer be if there were no blinds at the windows? Venetian blinds Light colored Double-pane window Heat-absorbing glass

4-83 Consider a building in New York (40°N latitude) that has 76 m² of window area on its south wall. The windows are double-pane heat-absorbing type, and are equipped with light-colored vene- tian blinds with a shading coefficient of SC = 0.30. Determine the total solar heat gain of the building through the south windows at solar noon in April. What would your answer be if there were no blinds at the windows? Venetian blinds Light colored Double-pane window Heat-absorbing glass

Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)

8th Edition

ISBN:9781305387102

Author:Kreith, Frank; Manglik, Raj M.

Publisher:Kreith, Frank; Manglik, Raj M.

Chapter8: Natural Convection

Section: Chapter Questions

Problem 8.44P

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1.11 Calculate the heat loss through a glass window 7-mm thick if the inner surface temperature is 20°C and the outer surface temperature is 17°C. Comment on the possible effect of radiation on your answer.
1.25 A spherical vessel, 0.3 m in diameter, is located in a large room whose walls are at 27°C (see sketch). If the vessel is used to store liquid oxygen at –183°C and both the surface of the storage vessel and the walls of the room are black, calculate the rate of heat transfer by radiation to the liquid oxygen in watts and in Btu/h.
1.26 Repeat Problem 1.25 but assume that the surface of the storage vessel has an absorbance (equal to the emittance) of 0.1. Then determine the rate of evaporation of the liquid oxygen in kilograms per second and pounds per hour, assuming that convection can be neglected. The heat of vaporization of oxygen at –183°C is .
1.80 Describe and compare the modes of heat loss through the single-pane and double-pane window assemblies shown in the sketch below. Problem 1.80
You are designing a chamber to contain the radiation emitted by nuclear decay during a fusion reaction. The left face of the (plane) chamber wall (x = 0) is exposed to the radiation and the right face of the wall (x = L) is perfectly insulated. To facilitate the fusion reaction, the left face of the wall is maintained at fixed temperature To. The radiation penetrates the wall causing uniform heat generation that varies with location inside the wall as ) = 40 (1 - 1) g(x) where qo [W/m^3 ] is a constant. Determine an expression for the temperature distribution in the wall T(x) assuming the thermal conductivity of the wall (k) is constant.
A brass plate has a circular hole whose diameter is slightly smaller than the diameter of an aluminum ball. Ifthe ball and the plate are always kept at the same temperature,(a) should the temperature of the system be increased or decreasedin order for the ball to fit through the hole? (b) Choose the bestexplanation from among the following:I. The aluminum ball changes its diameter more with temperature than the brass plate, and therefore the temperatureshould be decreased.II. Changing the temperature won’t change the fact that the ballis larger than the hole.III. Heating the brass plate makes its hole larger, and that willallow the ball to pass through.
An infrared camera is used to measure a temperature at a tissue location. The infrared camera uses the same equation as that in the lecture notes. When the total hemispherical emissivity is selected as &=1.0, the temperature reading on the camera is 45°C. (a) Based on the equation given in the notes, please calculate the radiation heat flux received by the camera qck. The Stefan-Boltzmann's constant ois 5.67*108 W/(m²K¹). (b) However, you notice that the actual emissivity of the tissue surface should be 0.95. The room temperature is 20°C. Use the equation again to calculate the temperature of the tissue location, note that qck should be the same as in (a). What is the absolute error of the measurement if both the room temperature and deviation from a perfect blackbody surface are not considered?
Find the percentage of reduction in heat transfer if the heater is completely covered by radiation shield (8= 0.05) and diameter 40 mm if a long cylindrical heater 30 in diameter is maintained at 700°C and has surface emissivity of 0.8. The heater is located in a large room whose wall is 35°C. Find the radiant heat transfer.
Liquefied natural gas (LNG) is transported around the globe using ships similar to thatshown in Figure QA3. This ship has four pressurised cylindrical steel tanks each ofradius of 20 m. The tanks are internally insulated with 30 cm of polyurethane foamwhich keeps the LNG at a constant -162 ºC. Take the effective sky temperature is 265K and the net radiative thermal energy exchange with the sky as 1x106 W. Calculate the surface temperature of the end (facing the sun) of a tank. Calculate the conductive heat transfer through the end (facing the sun)of a tank.
Question 3: An electronic device with a temperature of 84°C (shown in golden colour) is embedded inside a composite plastic tube which is equipped with three fins (shown in blue) to enhance the convective heat transfer with the surrounding air. The composite tube is held horizontally. The temperature drop along the fins can be ignored due to their high thermal conductivity. The outer ring of the fins (shown in brown) is insulated. The ambient temperature is 20°C. 3d. Calculate the heat transfer coefficients across the cylinder 3e. Calculate the heat transfer coefficients across the fins by assuming fins as vertical planes 31. Calculate the heat loss across the system Aluminium fins Diameter = 30 cm Insulated ring Thickness = 5 mm Composite tube Thickness = 5 mm Thermal conductivity = 25 W/mk Tube is held horizontally. Air 20°C Hot electronic device Temperature = 84°C Diameter = 10 cm Length = 100 cm %3D
Liquefied natural gas (LNG) is transported around the globe using ships similar to thatshown in Figure QA3. This ship has four pressurised cylindrical steel tanks each ofradius of 20 m. The tanks are internally insulated with 30 cm of polyurethane foamwhich keeps the LNG at a constant -162 ºC. Take the effective sky temperature is 265K and the net radiative thermal energy exchange with the sky as 1x10^6 W. (a) Calculate the surface temperature of the end (facing the sun) of a tank.(b) Calculate the conductive heat transfer through the end (facing the sun)of a tank. DATA FOR QUESTION: Thermal conductivity, polyurethane foam = 0.02 W/mKStefan’s Constant = 5.67x10^-8 W/m^2K^4Emissivity, steel = 0.95 answers: a) 375K b) 22.1kW
i. Calculate the heat loss through the furnace wall (all sides) by using conduction shape factor. ii. Calculate the heat loss through the furnace wall by using thermal resistance from each side (6 sides). iii. Determine the percentage difference of heat loss between case (i) and case (ii). iv. Explain why the heat transfer for both cases are different.